Adequate maintenance of rotating equipment is difficult to obtain because of extreme equipment duty cycles, the lessening of service factors, design and the lack of spare rotating equipment in many processing plants. This is especially true of process pumps, slurry pumps, machine tool spindles, wet end paper machine rolls, aluminum rolling mills and steam quench pumps and other equipment utilizing extreme contamination that can affect lubrication of the bearings of the rotating equipment.
Various forms of shaft sealing devices have been utilized to try to protect the integrity of the bearing environment, including rubber lip seals, clearance labyrinth seals, and attraction magnetic seals. Lip seals or O-ring shaft seals can quickly wear out and fail and are also known to permit excessive amounts of moisture and other contaminants to migrate into the lubricant (oil or grease) reservoir of the operating equipment even before failure had the interface between the rotor and the stator exposed to the contaminates or lubricants at the radial extremity of the seal.
Labyrinth-type seals involving closely related stator and rotor rings, which do not contact each other but define labyrinth passages between them have been devised and utilized and are illustrated in U.S. Pat. Nos. 4,706,968, 4,989,883, 5,069,461, and 6,419,233, the disclosures of which are incorporated by reference in their entireties.